This invention pertains to an elongated tool device adapted for remotely expanding a tubular sleeve into a surrounding tube to provide a seal therebetween. It pertains particularly to such a tool device containing dual internal pistons which are pressurized in sequence to expand collet fingers radially into the close-fitting sleeve and provide a leak-tight seal between the sleeve and surrounding tube.
Tubes in heat exchangers, particularly tubes in air preheaters used in fossil fuel fired steam power plants for preheating the combustion air against hot flue gas, often develop leaks after several years service due to metal corrosion, erosion or fatigue and require repair or replacement. Such tube leaks are usually located near the tubesheet but can occur anywhere along the tubes. Because replacement of tubes in such heat exchangers is quite expensive, particularly for large heat exchangers containing 10,000-50,000 tubes, and requires considerable outage time for a plant, a tool device method for reliably repairing such tubes quickly and inexpensively in a dusty environment has been needed.
Various devices for remotely expanding tubes into plates or tubesheets are known in the prior art. For example, U.S. Pat. No. 2,319,216 to Dewald discloses a pull-type tapered tube expander for expanding heat exchanger tubes into a tubesheet utilizing direct contact between a tapered wedge surface and the tube inner wall. U.S. Pat. No. 3,470,724 to Gregg discloses a pipe end forming machine which utilizes an external holding collet to hold a tube end and a central tapered arbor which is pushed through a forming collet to locally expand the tube end. U.S. Pat. No. 3,829,948 to Miller et al discloses an apparatus for expanding tubes into a tubesheet using an expandable collet. U.S. Pat. No. 4,182,152 to Vaill et al discloses a grid sleeve bulge tool used for securing internal guide tubes to an outer sleeve and grid. Also, U.S. Pat. No. 4,471,643 to Champoux et al discloses a tool adapted for pulling a tapered mandrel through a sleeve to secure together abutting workpieces. Furthermore, copending application Ser. No. 831,888 filed Feb. 24, 1986 discloses an elongated tube expander tool and method which is somewhat similar to the present invention.
The known prior art has various deficiencies, and has apparently not provided a self-contained tool device and method for remotely expanding a close-fitting tubular sleeve into a surrounding tube quickly and conveniently, so as to provide a pressure-tight joint therebetween. However, a tube repair method for inserting an elongated close-fitting metal sleeve into a tube and radially expanding and pressure sealing the sleeve to the tube inner wall by using an improved elongated pressure-operated tool device has now been developed according to the present invention.